The term “biodiesel” refers to a diesel-equivalent, processed fuel derived from biological sources, such as vegetable oils and/or animal fats. Biodiesel is a processed fuel that can be readily used in vehicles with diesel engines. Biodiesel can be used in pure form or may be blended with petroleum diesel at any concentration in most modern diesel engines.
Biodiesel typically includes the alkyl esters of fatty acids (or fatty acid alkyl esters). The alkyl group is commonly methyl, ethyl, propyl, or isopropyl, although it can also include higher numbers of carbon atoms. Fatty acid alkyl esters can be produced from fats or oils via catalyzed or uncatalyzed reactions. Many existing techniques for producing biodiesel rely on the use of relatively expensive high quality feed stocks such as soybean oil, which are usually greater than 99% triglycerides and 1% or less free fatty acids.
Since feed stock cost is a major component of the overall cost of producing biodiesel fuels, it can be significantly more economical to produce biodiesel from lower cost feed stocks. Unfortunately, many low cost feed stocks are not conducive to the biodiesel production processes. For example, some low cost feed stocks include contaminant materials that can interfere with the production process such as by plugging fixed bed flow reactors. Some low cost feed stocks are not readily solubilized and therefore may not be conducive to liquid phase processing through a fixed bed flow reactor.